Studies in the epidemiology of infectious myxomatosis of rabbits: VIII. Further observations on changes in the innate resistance of Australian wild rabbits exposed to myxomatosis

Abstract

1. In one Australian study area where the selection pressure of annual epizootics of myxomatosis has been extremely high, the innate resistance of the rabbits was found to have increased to such an extent that only 26% died when inoculated with a strain of myxoma virus which kills 88% of genetically unselected rabbits.2. The level of innate resistance in a rabbit population varies with the total experience of the disease.3. In combined field and laboratory trials it was shown that the mortality rate in the field is influenced by innate resistance at least as much as under the sheltered conditions of an animal house. The effect was apparent with both an attenuated and a highly virulent strain of virus.4. The moderately high ambient temperatures during the field experiments probably contributed to the sparing effect.